The invention relates to a folding machine for a web-fed printing press.
Folding machines for web-fed printing presses have a cutting blade cylinder, a folding blade cylinder and a folding jaw cylinder, whereby exemplars can be cut off from a web substrate with the help of the cutting blade cylinder. The exemplars cut off from the substrate are held by the folding blade cylinder and conveyed further in the direction of the folding jaw cylinder. Due to folding blades integrated into the folding blade cylinder, the exemplars can be inserted into folding jaws in the folding jaw cylinder, forming a fold. The folding jaw cylinder then conveys the exemplars for further processing.
Folding machines that can be operated in a so-called collecting mode are known as the state of the art. In collecting mode, two exemplars are collected and/or brought to an overlapping position on the folding blade cylinder, whereby an exemplar that has been cut from the substrate and is already being held against the folding blade cylinder is guided past the cutting point again and combined with a second cut exemplar on the folding blade cylinder. To prevent trimming, it is necessary here for the exemplars having only slightly differentiable sheet lengths to be separated alternately from the substrate. Thus, the exemplar separated first forms a so-called internal liner sheet after forming the fold; it has a slightly smaller sheet length than the second exemplar that is separated subsequently and is brought to overlapping with the insertion sheet on the folding blade cylinder, forming a so-called outer cover sheet.
German Patent Document No. 671 790 discloses a folding machine having a cutting blade cylinder, a folding blade cylinder and a folding jaw cylinder which can be operated in the collecting mode described above. To implement the separation of exemplars having slightly different sheet lengths, it is proposed according to this state of the art that two cutting blades or only a single cutting blade shall be assigned to the cutting blade cylinder, whereby the cutting blade or each cutting blade cooperates with the cutting strips assigned to the folding blade cylinder, and whereby the cutting strips and/or the cutting blade or each cutting blade is/are moved back and forth rhythmically. In German Patent Document No. 671 790 the alternating separation of exemplars with slightly different sheet lengths is implemented by the rhythmic movement of the cutting strips and cutting blades back-and-forth. The folding machine according to German Patent Document No. 671 790 has the disadvantage that additional drive units are required for the rhythmic movement of the cutting strips and cutting blades, causing a complex and therefore expensive design of the folding machine.
Against this background, the present invention is based on the problem of creating a novel folding machine for a web-fed printing press.
According to this invention, a separate drive is assigned to the cutting blade cylinder, whereby in collecting mode of the folding machine, the drive is operated non-uniformly to provide exemplars of different sheet lengths to be collected and is operated uniformly in non-collecting mode of the folding machine.
In collecting mode to separate an exemplar having a shortened sheet length before executing the separation step, the angular velocity of the cutting blade cylinder is preferably increased on the average, whereas for separating an exemplar having a lengthened sheet length, the angular velocity of the cutting blade cylinder is reduced on the average before executing the separating cut, whereby the angular velocity of the cutting blade cylinder is constant in execution of the particular separating cut and the circumferential speed is equal to the web speed.
Preferred refinements of this invention are derived from the following description. Exemplary embodiments of the invention are explained in greater detail with reference to the drawings without being restricted to this.